Ratchet pawl and mounting therefor



Nov. 2, 1954 L. A. JAMES ET AL RATCHET PAWL AND MOUNTING THEREFOR Filed June 13, 1952 INVENTOR. Lewis A. Uames and Duane A. James.

ATTORNEYS.

fiftates RATCHET PAWL AND MOUNTING THEREFOR Application .lune 13, 1952, Serial No. 293,312

7 Claims. (Cl. 74-116) This invention relates to ratchet mechanisms and more particularly to a ratchet pawl structure and mounting for effecting movement by increments of a driven structure such as control and/or timing devices in dishwashing machines and the like.

It is common practice to use pawls in ratchet structures wherein the pawl is a finger extending from a sleeve or hearing member rotatably mounted on an eccentric which is keyed to a drive shaft. In such structures the drive between the eccentric shaft and pawl is positive and if something happens that prevents the ratchet wheel from turning there will be breakage or other damage to the ratchet pawl and/or mountings therefor. Also in conventional ratchet structures, there usually is a second pawl suitably mounted in spaced relation to the driving pawl and arranged to engage the ratchet wheel to limit movement thereof to only the direction it is moved by the driving pawl. The use of two spaced pawls requires an adjustment and relative positioning for coordinated operation and such positioning can be difficult when the respective members are carried by separate portions of an assembly on which the ratchet mechanism is mounted.

The objects of the present invention are to provide a ratchet pawl structure which eliminates the aforesaid disadvantages; to provide a pawl of flat, relatively stiff spring material having an arcuate end extending substantially around an eccentric and/or sleeve thereon and resiliently and frictionally engaging same with suflicient force that with normal operating ratchet loads the pawl will advance the ratchet wheel and on abnormal, heavy loads the arcuate portion of the pawl will expand and release the eccentric or sleeve thereon sufiiciently so the eccentric may operate and the pawl will not advance the ratchet; to provide a pawl structure with an overload slip clutching action between the pawl and eccentric to render the pawl inoperative when heavy ratchet loads are encountered; to provide a combination driving pawl and stop pawl whereby the pawls cooperate to advance the ratchet wheel and prevent backward movement thereof; to provide resilient members acting on the pawls and a stationary abutment to urge the pawls into engagement with the teeth of the ratchet wheel; and to provide a ratchet pawl structure and mounting therefor which is economical to manufacture and assemble, of sturdy construction, efficient in operation and which reduces possibility of damage to equipment in the event of excessive overload or resistance to operation of the driven members.

In accomplishing these and other objects of the present invention, we have provided improved details of structure, the preferred forms of which are illustrated in the accompanying drawings, wherein:

Fig. 1 is an elevational view of a ratchet pawl structure and mounting embodying the features of the present invention.

Fig. 2 is a perspective view of the driving and stop pawl structures on a driving shaft.

Fig. 3 is a vertical sectional view through the driving and stop pawl structure and mounting as the driving pawl starts its advancing movement.

Fig. 4 is a vertical sectional view similar to Fig. 3 illustrating the relative position of the structure as the driving pawl is retracted.

Fig. 5 is a transverse sectional view taken on the line 5-'5, Fig. 4.

atent 2,693,115 Patented Nov. 2, 1954 Fig. 6 is a transverse sectional view taken on the line 6.6, Fig. 3

Referring more in detail to the drawings:

1 generally designates a portion of a machine or the like having a driving shaft 2 which is suitably rotated by a power means (not shown) and a driven shaft 3 to be advanced or rotated by increments at a substantial speed reduction relative to the driving shaft 2. The shaft 3 is rotatably mounted in suitable bearing brackets 4 carried by a plate 5 which is secured by suitable fastening devices 6 to a wall or frame 7. In the particular structure illustrated, a bevel gear 8 is fixed on the shaft 3 with the teeth of said gear meshing with teeth of a beveled gear 9 which is fixed relative to a ratchet wheel 10. The ratchet wheel It is mounted on a shaft 11 suitably mounted on the machine structure with the axis of said shaft parallel to and spaced from the axis of the driving shaft 2, the driving shaft 2 being rotatably carried by the machine member 7 and rotated in a clockwise direction, Fig. 1.

A pawl assembly 12 is carried on the driving shaft 2 and has suitable engagement with faces 13 of teeth 14 on the periphery of the ratchet wheel ll whereby operation of the pawl assembly 12 in response to rotation of the drive shaft 2 advances or rotates the ratchet wheel 10 by increments in the same direction as the rotation of the driving shaft 2, that is in a clockwise direction, Fig. 1. An eccentric 15 is provided with a bore 16 for receiving the driving shaft 2, said eccentric being secured to said driving shaft by a suitable key, for example a setscrew l7, screwed into a threaded radial bore 18 extending from the periphery 19 of the eccentric to the bore 16. The eccentric i5 is preferably substantially in alignment with a ratchet wheel 10 and is spaced as at 20 from the machine member 7.

A driving pawl 21, preferably formed of flat, relatively stiff spring material, has an arcuate end 22 formed thereon which, in the illustrated form, is slightly more than three-fourths of a circle. The arcuate end is expanded over the outer periphery of a sleeve 23 which has a bore 24 rotatably engaging the periphery ll? of the ec centric 15. The sleeve 23 serves as a bearing sleeve and. the arcuate end 22 of the pawl 21 resiliently engages the sleeve to form a friction drive therebetween that will slip and permit relative movement when the pawl encounters excessive loads. The sleeve and arcuate end are provided with registrable apertures 25 and 26 respectively to provide access to the screw 17 for securing the eccentric to the driving shaft 2. The pawl 21 has a finger portion 27 extending from the arcuate end 22 and of sumcient length to suitably engage the teeth 14 of the ratchet wheel 10.

The finger portion 27 extends from the arcuate end 22 of the pawl in the direction of rotation of the shaft 2 whereby rotation of said shaft tends to rotate the pawl and maintain the free end 23 of same in engagement with the teeth on the periphery of the ratchet wheel 1% It is preferable that the end 28 of the finger portion 27 engage the ratchet wheel slightly short of the point of. contact of a line through the axis of the shaft 2 and tangent to the ratchet wheel when said pawl is at the end of its ratchet wheel advancing movement as shown in Fig. 1. It is also preferable that the throw of the eccentric 15 and the spacing of the ratchet wheel teeth be correlated whereby upon each revolution of the eccentric the ratchet wheel will be advanced slightly more than the spacing of two or more teeth.

The pawl structure described may be utilized with a conventional second pawl engaging the teeth of the ratchet wheel to prevent backward movement thereof whereby the pawl structure will advance said ratchet wheel and provide an overload slip clutching action between the pawl and eccentric when abnormal, heavy loads on the driven member are encountered. in the structure illustrated, a stop pawl 2? is suitably formed to provide a finger 30 slightly wider than the driving pawl finger portion 27 and having side flanges 31. forming a channel 32 in which the driving pawl may move. Gne end .33 of the finger 30 is adapted to engage the teeth 14 .of the ratchet wheel 16. Adjacent the other end of the :finger 30 the flanges 31 are provided with extensions ice forming ears 34 straddling the eccentric 15 and arcuate end 22 of the driving pawl. The ears 34 are provided with aligned bores 35 of suitable size to sleeve over the driving shaft 2. It is preferable that the portions of the ears 34 adjacent to and surrounding the bores 35 be embossed or otherwise formed to increase the bearing contact of the edges of the bores 35 with the shaft 2. The contact of the edges of the bores 35 with the shaft 2 causes the rotation of said shaft to tend to urge the end 33 of the stop finger 3t) into engagement with the ratchet wheel 10.

The stop finger 3G is of such length that the end 33 thereof extends beyond the end 28 of the driving pawl slightly less than the spacing of the teeth 14 on the ratchet wheel when the driving pawl is at the end of its ratchet wheel advancing movement as shown in Fig. 1. To further aid in maintaining the ends of the pawl fingers in engagement with the teeth of the ratchet wheel 10, resilient members are arranged in engagement with the respective pawl fingers to tend to swing same in the direction of rotation of the eccentric 15. A resilient member 36 preferably in the form of a flat spring has one end secured to the stop finger 30 adjacent the drive shaft 2 and the other free end 37 thereof resiliently engaging the drive pawl 2t between the shaft 2 and the end 28 of said pawl. A second resilient member 38, preferably a fiat spring, has one portion secured to the stop pawl 30 adiacent the end 33 thereof and the free end of said resilient member extending from adjacent the end 33 of said pawl at an angle thereto and resiliently engaging an abutment or flange 40 suitably secured to the plate 5. With this arrangement there is an accurate, relative positioning of the driving and stop pawls at all times and the ends of said pawls are maintained in engagement with the teeth of the ratchet wheel 10.

In the operation of a ratchet pawl assembly constructed as described with power applied to rotate the driving shaft 2 the eccentric 15 rotates inside of the sleeve 23 which due to the resilient and frictional engagement of the arcuate end 22 of the driving pawl 21 tends to swing the finger 27 in the direction of rotation of the eccentric, that is clockwise, Fig. 3. Also the rotation of the eccentric 15 effects reciprocation of the driving pawl finger 27 whereby the end 28 thereof engaged with the teeth 14 of the ratchet wheel advances or rotates said wheel in increments substantially equal to the throw of the eccentric. During the retraction movement of the driving pawl finger in the reciprocation thereof, the end 33 of the stop pawl finger 30 will engage a tooth of the ratchet wheel and since the ears 34 on the stop pawl are mounted on the shaft 2 rotation of said shaft tends to maintain the end 33 of said stop finger in engagement with the tooth of the ratchet wheel and prevent backward movement of said wheel. The resilient member 38 due to its engagement with the stop pawl and abutment 443 further tends to maintain the stop pawl in engagement with the teeth of the ratchet wheel. The resilient member 36 due to its engagement with the stop pawl and driving pawl tends to further maintain engagement of the driving pawl with the teeth of the ratchet wheel.

If excessive loads are applied to the driven shaft 3 to abnormally resist rotation thereof, the increased forces acting on the driving finger 27 will expand the arcuate portion 22 and the eccentric may rotate without effecting further advancing movement of the driving pawl whereby the tension of the arcuate member 22 serves to limit the driving force applied to the teeth of the ratchet wheel. In the event of change in position of parts on the machine due to adjustment or the like the relationship between the ends of the driving and stop pawls will not be altered. Therefore the pawl structure is not subject to variations as would occur if the pawl members were mounted on separate portions of the structure.

It is believed obvious we have provided an improved ratchet pawl structure and mounting therefor which is efficient in operation, maintains relative relationship between the driving and stop pawls and has an overload release to protect the machine structure from damage. What we claim and desire to secure by Letters Patent 1s:

1. A ratchet wheel mechanism comprising, a support, a ratchet wheel rotatably mounted on the support and having teeth on the periphery thereof, an eccentric rotatable on an axis parallel to and spaced from the axis of rotation of said ratchet wheel and substantially in the same plane as said wheel, means rotating said eccentric, a bearing sleeve rotatably mounted on the eccentric, an open-ended arcuate resilient member extending around and frictionally engaging the periphery of the bearing sleeve, and a driving pawl finger on said arcuate member and extending therefrom in the direction of rotation of the eccentric and having a free end engaging the teeth of the ratchet wheel whereby rotation of the eccentric reciprocates the driving pawl and advances the ratchet wheel by increments, the resiliency of the arcuate resilient member being such that predetermined resistance to rotation of the ratchet wheel imparts forces to the driving pawl finger to expand the arcuate resilient member and release same sufiiciently whereby the eccentric may revolve without reciprocating the driving pawl finger.

2. A ratchet wheel mechanism comprising, a support, a ratchet wheel rotatably mounted on the support and having teeth on the periphery thereof, a rotating driving shaft mounted on the support is spaced parallel relationship to the axis of rotation of said ratchet wheel, an eccentric fixed on the driving shaft in alignment with the ratchet wheel, a bearing sleeve rotatably mounted on the eccentric, an open-ended arcuate resilient member extending around and frictionally engaging the periphery of the bearing sleeve, a driving pawl finger extending from one end of said arcuate resilient member in the direction of rotation of the eccentric and having a free end engaging the teeth of the ratchet wheel whereby rotation of the eccentric reciprocates the driving pawl and advances the ratchet wheel by increments, the resiliency of the arcuate resilient member being such that predetermined resistance to rotation of the ratchet wheel imparts forces to the driving pawl finger to expand the arcuate resilient member and release same sufficiently whereby the eccentric may revolve without reciprocating the driving pawl finger, and means engaging the ratchet wheel to stop rotation thereof rearwardly relative to the direction said wheel is advanced by the driving pawl.

3. A ratchet wheel mechanism comprising, a support, a ratchet wheel rotatably mounted on the support and having teeth on the periphery thereof, a rotating driving shaft mounted on the support in spaced parallel relationship to the axis of rotation of said ratchet wheel, an eccentric fixed on the driving shaft in alignment with the ratchet wheel, a bearing sleeve rotatably mounted on the eccentric, an open-ended arcuate resilient member extending around and frictionally engaging the periphery of the bearing sleeve, a driving pawl finger on said arcuate member and extending therefrom in the direction of rotation of the eccentric and having a free end engaging the teeth of the ratchet wheel whereby rotation of the eccentric reciprocates the driving pawl and advances the ratchet wheel by increments, the resiliency of the arcuate resilient member being such that predetermined resistance to rotation of the ratchet wheel imparts forces to the driving pawl finger to expand the arcuate resilient member and release same sufliciently whereby the eccentric may revolve without reciprocating the driving pawl finger, and a stop pawl engaging the teeth of the ratchet wheel to stop rotation thereof rearwardly relative to the direction said wheel is advanced by the driving pawl.

4. A ratchet wheel mechanism comprising, a support, a ratchet wheel rotatably mounted on the support and having teeth on the periphery thereof, an eccentric rotatable on an axis parallel to and spaced from the axis of rotation of said ratchet wheel and substantially in the same plane as said wheel, means rotating said eccentric, a bearing sleeve rotatably mounted on the eccentric, an open-ended arcuate resilient member extending around and frictionally engaging the periphery of the bearing sleeve, a driving pawl finger on said arcuate member and extending therefrom in the direction of rotation of the eccentric and having a free end engaging the teeth of the ratchet Wheel whereby rotation of the eccentric reciprocates the driving pawl and advances the ratchet wheel by increments, the resiliency of the arcuate resilient member being such that predetermined resistance to rotation of the ratchet wheel imparts forces to the driving pawl finger to expand the arcuate resilient member and release same sufficiently whereby the eccentric may revolve without reciprocating the driving pawl finger, a stop pawl finger, and spaced ears on the stop pawl finger rotatably mounted on the eccentric rotating means, said stop pawl finger extending generally in the same direction as the driving pawl finger and having a free end engaging the teeth of the ratchet wheel adjacent the free end of the driving pawl finger to stop rotation of said ratchet wheel rearwardly relative to the direction said wheel is advanced by the driving pawl.

5. A ratchet wheel mechanism comprising, a support, a ratchet wheel rotatably mounted on the support and having teeth on the periphery thereof, a rotating driving shaft mounted on the support in spaced parallel relationship to the axis of rotation of said ratchet wheel, an eccentric fixed on the driving shaft in alignment with the ratchet wheel, a bearing sleeve rotatably mounted on the eccentric, an open-ended arcuate resilient member extending around and frictionally engaging the periphery of the bearing sleeve, a driving pawl finger extending from one end of said arcuate resilient member in the direction of rotation of the eccentric and having a free end engaging the teeth of the ratchet wheel whereby rotation of the eccentric reciprocates the driving paw and advances the ratchet wheel by increments, the resiliency of the arcuate resilient member being such that predetermined resistance to rotation of the ratchet wheel imparts forces to the driving pawl finger to expand the arcuate resilient member and release same sufiiciently whereby the eccentric may revolve without reciprocating the driving pawl finger, a stop pawl finger, and spaced ears on the stop pawl finger and having aligned bearing openings through which the driving shaft extends to rotatably mount the stop pawl finger thereon, said s pawl finger extending generally in the same direction as the driving pawl finger and having a free end engaging the teeth of the ratchet wheel adjacent the free end of the driving pawl finger to stop rotation of said ratchet wheel rearwardly relative to the direction said wheel is advanced by the driving pawl.

6. A ratchet wheel mechanism comprising, a support, a ratchet wheel rotatably mounted on the support and having teeth on the periphery thereof, a rotating driving shaft mounted on the support in spaced parallel relationship to the axis of rotation of said ratchet wheel, an eccentric fixed on the driving shaft in alignment with the ratchet wheel, a bearing sleeve rotatably mounted on the eccentric, an open-ended arcuate resilient member extending around and frictionally engaging the periphery of the bearing sleeve, a driving pawl finger on said arcuate member and extending therefrom in the direction of rotation of the eccentric and having a free end engaging the teeth of the ratchet wheel whereby rotation of the eccentric reciprocates the driving pawl and advances the ratchet wheel by increments, the resiliency of the arcuate resilient member being such that predetermined resistance to rotation of the ratchet wheel imparts forces to the driving pawl finger to expand the arcuate resilient member and release same sufficiently whereby the eccentric may revolve without reciprocating the driving pawl finger, a stop pawl finger, spaced side flanges on the stop pawl straddling the driving pawl finger, spaced ears on the stop pawl finger and having aligned bearing openings through which the driving shaft extends to rotatably mount the stop pawl finger thereon, said stop pawl finger extending generally in the same direction as the driving pawl finger and having a free end engaging the teeth of the ratchet wheel adjacent the free end of the driving pawl finger to stop rotation of said ratchet wheel rearwardly relative to the direction said wheel is advanced by the driving pawl, an abutment on the support adjacent the free end of the stop pawl finger, and resilient members engaging the driving pawl finger, stop pawl finger and abutment for urging the free ends of the respective pawl fingers into engagement with the teeth of the ratchet wheel.

7. A ratchet wheel mechanism comprising, a support, a ratchet wheel rotatably mounted on the support and having teeth on the periphery thereof, an eccentric means rotatable on an axis parallel to and spaced from the axis of rotation of said ratchet wheel and substantially in the same plane as said wheel, said eccentric means having a cylindrical periphery, means rotating said eccentric, an open ended arcuate resilient member extending around and frictionally engaging the cylindrical periphery of the eccentric means, and a driving pawl finger on said arcuate member and extending therefrom in the direction of the eccentric means and having a free end engaging the teeth of the ratchet wheel, said open end of the arcuate member being adjacent to the driving pawl finger whereby rotation of the eccentric means reciprocates the driving pawl and advances the ratchet wheel by increments, the resiliency of the arcuate resilient member being such that predetermined resistance to rotation of the ratchet wheel imparts forces to the driving pawl finger to expand the arcuate resilient member and release same sufiiciently whereby the cocentric means may revolve without reciprocating the driving pawl finger.

Refereuces Cited in the file of this patent UNITED STATES PATENTS Number Name Date 554,890 Meier Feb. 18, 1896 1,913,184 Zubaty June 6, 1933 2,595,967 McCloy May 6, 1952 FOREIGN PATENTS Number Country Date 756,950 France Dec. 18, 1933 

